Sequential sputtering apparatus

ABSTRACT

INCREASED PRODUCTION YIELDS WITH RELATIVE SAVINGS IN TIME AND EXPENSE ARE MADE POSSIBLE WITH SPUTTERING APPARATUS USED IN COATING SELECTED SURFACES OF OBJECTS, SUCH AS THE CUTTING EDGES OF RAZOR BLADES IN WHICH PROVISION IS MADE FOR SEQUENTIALLY PRESENTING A PLURALITY OF OBJECTS TO CATHODE-SPUTTER TARGETS FOR COATING. TWELVE BAYONETS, EACH ADAPTED TO HOLD AS MANY AS 1500 RAZOR BLADES, ARE EQUALLY SPACED ABOUT THE PERIPHERY OF A ROTATABLE DRUM. BY MEANS OF AN EPICYCLIC HAIN AND GEAR TRAIN, EACH   BAYONET ROTATES 1/2 REVOLUTION WITH RESPECT TO THE DRUM DURING EACH REVOLUTION OF THE DRUM. THIS PERMITS THE COATING OF OPPOSING SURFACES OF EACH OF THE OBJECTS TO BE COATED IN A MAXIMUM OF TWO DRUM REVOLUTIONS WHICH, IN THE INSTANT CASE, IS 36 MINUTES FOR COATING THE CUTTING EDGES OF DOUBLE EDGED RAZOR BLADES WITH 600 A. OF CHROMIUM.

Feb. 9, 1971 sKlNNER ET AL 3,562,149

SEQUENTIAL SPUTTERING APPARATUS Filed 00L 23, 1967 3 Sheets-Sheet VACUUM SYSTEM INVENTORS JAMES R. SKINNER LAWRENCE F. HER

FIG.| BY A Feb. 9, 1971 J SK|NNER ET AL 3,562,14Q

SEQUENTIAL SPUTTERING APPARATUS Filed Oct; 23, 1967 3 sw m-sheet 2 N K] N I {No FIG 2 Feb. 9, 1971 SK|NNER ET AL 3,562,140

SEQUENTIAL SPUTTERING APPARATUS 3 Sheets-Sheet 5 Filed Oct. 23, 1967 INVENTORS JAMES R. SKINNER LAWRENCE E HERTE ATTORNY United States Patent Oifice 3,562,140 SEQUENTIAL SPUTTERING APPARATUS James R. Skinner, Cupertino, and Lawrence F. Herte, Palo Alto, Calif., assignors, by mesne assignments, to Eversharp, Inc., Milford, Conn., a corporation of Delaware Filed Oct. 23, 1967, Ser. No. 677,160 Int. Cl. C23c /00 US. Cl. 204-298 6 Claims ABSTRACT OF THE DISCLOSURE Increased production yields with relative savings in time and expense are made possible with sputtering apparatus used in coating selected surfaces of objects, such as the cutting edges of razor blades in which provision is made for sequentially presenting a plurality of objects to cathode-sputter targets for coating. Twelve bayonets, each adapted to hold as many as 1500 razor blades, are equally spaced about the periphery of a rotatable drum. By means of an epicyclic chain and gear train, each bayonet rotates /2 revolution with respect to the drum during each revolution of the drum. This permits the coating of opposing surfaces of each of the objects to be coated in a maximum of two drum revolutions which, in the instant case, is 36 minutes for coating the cutting edges of double edged razor blades with 600 A. of chromium.

BACKGROUND OF THE INVENTION The present invention relates in general to sputtering apparatus and in particular to apparatus for sequentially coating the cutting edges of a plurality of cutting instruments, for example, doubled edged razor blades, or coating plural surfaces of other items, such as the opposite surfaces of silicon wafers used in electronic devices.

Sputtering apparatus of the described type is known in which the cutting edges of razor blades in stacks are presented sequentially to a sputtering target for predetermined time intervals. After one cutting edge of the blades is coated, the stacks are rotated 180 degrees for presenting the opposite cutting edge of the blades to the targets for another predetermined sputtering interval. After both edges of a double edged blade are coated, the apparatus must be brought up to air, loaded with three more stacks of blades and then evacuated in preparation for another sputtering cycle. The time required for a pump down cycle, that is, for sputter coating both edges, bringing the system up to air, reloading and re-evacuating the system, as well as the limited size of available sputtering targets, all together limits the number of blades which can be processed in a days production run.

SUMMARY OF THE INVENTION With the present invention, the cutting edges of as many as 18,000 razor blades may be coated with approximately 600 A. of chromium during a 36 minute sputtering interval wherein one cutting edge of each blade is exposed for coating for a period of approximately three minutes.

As more specifically described hereinafter, twelve bayonets, each with 1500 blades, are disposed about the periphery of a rotatable flanged drum which is driven by means of a chain coupled to a motor. Each of the bayonets is held in cantilever fashion by a rotatable flanged member which is in turn itself rotated by a chain drive coupled to a stationary sprocket located at the axis of the drum. As the drum rotates about its axis, each of the bayonets are thus forced to rotate about its own axis. Thus, the angular motion of the drum and bayonets rela- Patented Feb. 9, 1971 tive to the surrounding apparatus may be said to be epicyclic in nature such that in two complete revolutions of the drum both cutting edges of each of the blades is presented to the sputter targets for coating by deposition of material sputtered from the targets. The angular velocity of the drum is such that each cutting edge is exposed for coating for a three minute interval; the interval required being a function of the material sputtered and the thickness of the coating desired.

While the number of blades coated per instant of time is one third the number coated simultaneously in prior known apparatus, the number being coated per pump down cycle is increased by a factor of 4 'with a resulting savings in downtime and the expense encountered in preparing the apparatus for coating successive batches of blades.

Accordingly, a primary object of the present invention is an improved sputtering apparatus for coating different surfaces of an item to be coated, for example, coating plural cutting edges of cutting instruments, which apparatus greatly increases the number of items which may be coated per pumpdown cycle.

Another object of the invention is sputtering apparatus as described which used a rotatable drum, attached to the periphery of which are a plurality of rotatable bayonets for holding the objects to be coated.

Other objects, features and advantages of the invention will be apparent from the detailed description hereinafter when considered in connection with the accompanying drawings in which:

FIG. 1 is a fragmentary view partially broken away of apparatus embodying the present invention,

FIG. 2 is a cross sectional view taken along line 2-2 of FIG. 1,

FIG. 3 is cross sectional view taken along line 33 of FIG. 2,

FIG. 4 is an enlarged detail view of the bayonet-razor blade assembly; and

FIG. 5 is an enlarged view taken on the line 5-5 of FIG. 2.

Referring to FIG. 1 there is shown sputtering apparatus embodying the present invention enclosed within a vacuum chamber 1 comprised of a bell jar 2 seated in a vacuum tight manner on a stainless steel spool vacuum manifold 3. An anodized aluminum frame 4 fastened to manifold 3 in any well known manner supports a rotatable drum 5 provided at one end with a radially extended flange 6. Flange 6 is provided with a plurality of equally spaced apertures, which are located about the drum and are adapted to hold a plurality of rotatable arbors 7 into each of which may be inserted a removable bayonet assembly 8 previously loaded with as many as 1500 razor blades 9 as seen in FIGS. 2 and 4.

Attached to drum 5 at its axis on the end opposite flange 6, there is provided a sprocket 10 which is coupled to a motor 11 by means of a chain 12. For reasons given hereinafter, motor 11 is adapted to have an output speed of .13 rpm. such that drum 5 is angularly displaced 60 degrees every three minutes.

A sputtering module 13 including targets 14 consisting of any desirable coating material, for example, chromium, is disposed directly above drum 5. A shield 15 is attached to the bottom of module 13 to restrict the sputtering of target material to only those blades 9 which are exposed to and horizontally positioned beneath module 13.

In the preferred sputtering apparatus, as discussed in copending application Ser. No. 625,733, filed Mar. 24, 1967 and assigned to the same assignee as the instant application, a glOW discharge is developed between targets 14 by means of electrical energy applied to target electrodes 14' to which targets 14 are attached. Separate target electrodes 14 are required when targets 14 consist of nonconductive or dielectric material, such as quartz. When the targets 14 are of chromium, as described herein, the electrical energy could be applied directly to the targets.

In either case, ions developed within the discharge are accelerated toward and strike targets 14 whereupon electrically neutral target material is ejected and deposited on surrounding surfaces, such as, the cutting edges of blades 9.

With the exception of targets 14, target electrodes 14 and associated electrical circuitry, the structure including drum and blades 9 are maintained at ground potential as is true of a well developed glow discharge. Sinc the sputtered material is electrically neutral, it will deposit on any surface; however, the ground plane is necessary in order to prevent sputtering of surrounding structure as would occur if the surrounding structure were permitted to take on a negative potential relative to the glow discharge.

In practice, however, it has been found that the potential of the glow discharge does vary positively and negatively with respect to ground. In order to minimize any resulting undesired sputtering of surrounding structure, materials of low sputtering rate, such as, anodized aluminum are used for the parts on which sputtering would be undesirable. It should be understood that although a specific two-electrode sputtering apparatus is disclosed, other suitable sputtering apparatus could be employed, such as conventional sputtering apparatus employing a single target.

Referring to FIG. 2, there is shown the drum 5 supported at each end by frame 4. Motor 11, mounted on manifold 3 is coupled to chain 12 by means of a sprocket :16. Bayonet assemblies 8, described more fully with respect to FIG. 4, are inserted in the rotatable arbors 7 for rotation with the arbors. The arbors 7 are driven by sprockets 17, shown in FIGS. 3 and 4. Sprockets 17 are coupled to a stationary sprocket 18, shown in FIG. 3 by means of a second chain 19. The sprocket 18 is positioned on the axis of drum 5 but is rigidly attached to the left frame portion 4 so it will not rotate. A shield 20* is provided about sprockets 17 and 18, and chain 19 to prevent their being coated by sputtered material.

Referring to FIG. 3, there is shown the plurality of equally spaced apart sprockets 17 each of which is coupled to one of the rotatable arbors 7 for imparting rotary motion to bayonets 8. The ratio of the number of teeth or gear ratio of sprockets 17 and 18 is 2:1 such that each of the sprockets 17 revolves /2 revolution relative to the drum 5 for each revolution of the drum, and 1 /2 revolutions relative to the sputtering targets 14 for each revolution of the drum.

The arrows shown on each of sprockets 17 in FIG. 3 indicate the relative orientation of bayonet assemblies 8 at any instant in time as further shown in FIG. 1.

With reference to sprockets A, B, C, etc., of sprockets 17 it can be seen in FIG. 3 that as drum 5 revolves counterclockwise, bayonet assemblies 8 and the blades 9 associated with each of them will be sequentially exposed to targets 14 such that one edge of each of blades 9 will be coated within one drum revolution. At the beginning of the second drum revolution, the second edge of blades 9 associated with sprocket A will be coated.

Thus, after 2 complete revolutions of drum 5, both cutting edges of all the blades 9 will be exposed to targets 14 for coating.

In practice, the time required to lay down 600 A, of chromium on the cutting surface of blades 9 is three minutes. Obviously, other time intervals with other materials and thickness may be used depending on the density of the plasma used in generating the ions needed for sputtering as well as the electrical parameters selected for operating the targets.

In FIGS. 4 and 5 there is shown a particular arrangement for bayonets 8. A narrow flat elongated metal strip or plate 21 is slotted at one end and adapted to receive a holding fixture or bracket 22. Bracket 22 is made in two pieces which fit on opposite sides of the strip 21, as shown in FIG. 1. The two pieces of bracket 22 are held together by a tightening screw 23 which may be loosened to allow bracket 22 to be slipped off of the end of plate 21 for loading and unloading of successive stacks of razor blades 9. Bracket 22 is further adapted to hold the blades 9 firmly in place adjacent one another or to hold the blades 9 loosely to permit cleaning by such means as ultrasonic baths. The end of plate 21 opposite bracket 22 is fixed in any well known manner to a second bracket 25 provided with a shaft 26 having a detent for receiving a spring loaded ball catch 27 mounted in each arbor 7. Bracket 25 is further provided with an aligning and driving dowel 28 which slides into a recess provided in each arbor 7.

In operation, a supply of bayonets 8 may be provided at an assembly line station. As a stack of 1500 razor blades are formed, the stack may be speared with plate 21. Bracket 22 is then placed over the slotted end of plate 21 and tightened to firmly hold the blades 9 in place. The loaded bayonets 8 are then inserted in arbors 7 and chamber 1 is evacuated to a pressure of approximately 10* torr after which sputtering is started.

During sputtering, drum 5 is rotated by motor 11 at a rate of 20 degrees per minute such that each cutting edge of each blade is exposed to targets 14 for sputtering for an interval of about 3 minutes. As drum 5 revolves, each of arbors 7 together with bayonets 8 are in turn rotated by virtue of the chain 19 coupling stationary sprocket 18 to each one of sprockets 17. The resulting epicyclic motion of the bayonets 8 relative to the targets 14 is such that both edges of each of blades 9 is exposed to targets 14 for coating for a three minute interval. Since in the preferred embodiment twelve bayonets are used, the total elapsed sputtering time is 36 minutes.

With the number of bayonets used, the time for loading and evacuating the system becomes in proportion a smaller period relative to the working or sputtering time resulting in a considerable increase in production with considerable savings in time and expense.

Clearly, the described apparatus and specifically the described bayonets 8 may be modified for receiving other types of objects for coating. All that is necessary is that the objects be restrained from falling as the arbors 7 are rotated.

If more than two surfaces are desired to be coated, modification of the gear ratios is possible such that successive surfaces are exposed to targets 14 during successive revolutions of the drum 5.

In addition to the above-suggested alternative arrangements, other materials, such as tungsten, quartz and hydrocarbon compounds may be used to coat the objects to selected thickness. In addition, the desiredcoating can be deposited by means other than sputtering, such as spraying.

Accordingly, the above description and accompanying drawing are to be taken as only illustrative and not as limiting the scope of the invention as hereinafter defined in the claims.

What is claimed is:

1. An apparatus for coating a plurality of selected surfaces of a plurality of objects with selected material comprising:

means for depositing said selected material on said objects;

moveable means for holding said objects;

first means for moving said holding means along a continuous path repeatedly past said depositing means for coating said objects;

second means for moving said holding means relative to said first moving means for coating a plurality of said selected surfaces;

said second moving means comprising an attachment connecting said holding means to said first moving means for rotation of said holding means relative to said first moving means about an axis of rotation which travels with said first moving means;

said depositing means being positioned to direct the deposit toward the side of said axis of rotation; and

means for driving said first and second moving means to present a different partial surface of said object to said depositing means on diiferent passes of said holding means past a given point adjacent said depositing means along said continuous path.

2. An apparatus according to claim 1 wherein said moveable holding means comprises a plurality of bayonet assemblies;

said first moving means comprises a radially projecting flange member, means supporting said flange for rotation about its axis, and means for rotating said flange; and

said attachment between said first and second moving means comprises a plurality of spaced apart arbors disposed about and rotatably supported in said flange and adapted to receive and removably hold said plurality of bayonet assemblies in cantilever fashion, and means for rotating said arbors relative to said flange.

3. An apparatus according to claim 2 wherein said means for rotating said arbors comprises a sprocket attached to each of said rotatable arbors, a stationary sprocket positioned coaxial with said flange, and a drive chain connecting said stationary sprocket to each of said sprockets on the arbors.

4. An apparatus according to claim 2 wherein said means for rotating said arbors causes each arbor to rotate degrees relative to said flange during each complete revolution of said flange.

5. An apparatus according to claim 2 wherein said means for supporting said flange comprises a drum, said flange being positioned adjacent one end of said drum and said bayonet assemblies being positioned to surround said drum.

6. An apparatus according to claim 1 wherein said depositing means comprises means for sputtering, and said first and said second moving means are operated continuously and simultaneously during sputtering.

References Cited UNITED STATES PATENTS 357,515 2/1887 Wood et al. 118319 1,474,999 11/1923 Coates 118-319 1,485,925 3/1924 Hogenson 118-319 2,324,890 7/1943 Temple 1183 19 2,847,325 8/1958 Riseman et al. 204192 3,206,322 9/ 1965 Morgan 204298 ROBERT K. MIHALEK, Primary Examiner US. Cl. X.R. 

